Description

   The va_arg function interprets the object at the address
   specified by the list incrementor according to type. If there
   is no corresponding argument, the behavior is undefined.

   When using va_arg to write portable applications, include the
   <stdarg.h> header file (defined by the ANSI C standard), not the
   <varargs.h> header file, and use va_arg only in conjunction with
   other functions and macros defined in <stdarg.h>.

   For an example of argument-list processing using the <stdarg.h>
   functions and definitions, see the "Character, String, and
   Argument-List Functions" chapter of the VSI C RTL Reference
   Manual.